It would warm our hearts (a strange metaphor) to believe that we have the power to determine our own level of achievement. And to at least a minor extent we do. Here is a link to a brief account of a meta-study of the many pieces of research establishing and analyzing the extent of the correlation between practice and achievement. Gladwell popularized the idea that 10,000 hours of practice is the common stimulus for excellence in your chosen activity. Many of us rushed to embrace this psychologically comforting idea. Lionel Messi did not become the best football player in the world primarily via practice. Andrea Bocelli did not achieve the ability to bring tears to the eyes of listeners with the incredible sounds emerging from his mouth primarily via practice.
No, the world, as many of us suspect, is not very fair. A few have something the rest of us can only admire from afar. BUT we all can benefit somewhat from analytical practice sessions. That last point seems to be all the good news we can reasonably justify.
When you look at the link I hope you enjoy as much as I do the brief mention that the positive correlation between success and practice is much stronger when practice time is measured by the amount of time the person REMEMBERS HAVING PRACTICED. The correlation falls when the measurement is derived from logs of actual practice time.